Patient interfaces

ABSTRACT

The present invention relates to a device for delivering a supply of gases to a patient. The device includes a patient interface and connecting member. The connecting member is preferably a L-shaped swiveled connector that is capable of being fixed into one of two positions, a first position where the connector is freely rotatable within the patient interface, and a second position where an interference between the interface and connector prevents the free rotation of the connector within the patient interface, The present invention further relates to a connector that has outlet means, which includes at least one outlet vent and a funnel, which in use directs and passes a substantial portion gases expired from the patient through the outlet vent or vents.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/536,656 filed on Aug. 6, 2009, which is acontinuation application of U.S. patent application Ser. No. 10/916,700filed on Aug. 12, 2004, now U.S. Pat. No. 7,874,292 issued on Jan. 25,2011, which is a divisional application of U.S. patent application Ser.No. 10/293,637 filed on Nov. 13, 2002, now U.S. Pat. No. 6,892,729issued on May 17, 2005, which was reissued as U.S. reissue applicationSer. No. 11/973,896 filed on Oct. 10, 2007, now RE41298 issued on May 4,2010. Each of these are hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to patient interfaces, particularly though notsolely for use in providing Continuous Positive Airway Pressure (CPAP)therapy or positive pressure ventilation to patients suffering fromobstructive sleep apnoea (OSA).

2. Summary of the Related Art

In the art of respiration devices, there are well known a variety ofrespiratory masks which cover the nose and/or mouth of a human user inorder to provide a continuous seal around the nasal and/or oral areas ofthe face such that gas may be provided at positive pressure within themask for consumption by the user. The uses for such masks range fromhigh altitude breathing (i.e., aviation applications) to mining and firefighting applications, to various medical diagnostic and therapeuticapplications.

One requisite of such respiratory masks has been that they provide aneffective seal against the patient's face to prevent leakage of the gasbeing supplied. Commonly, in prior mask configurations, a goodmask-to-face seal has been attained in many instances only withconsiderable discomfort for the user. This problem is most crucial inthose applications, especially medical applications, which require theuser to wear such a mask continuously for hours or perhaps even days. Insuch situations, the user will not tolerate the mask for long durationsand optimum therapeutic or diagnostic objectives thus will not beachieved, or will be achieved with great difficulty and considerableuser discomfort.

Where such masks are used in respiratory therapy, in particulartreatment of obstructive sleep apnoea (OSA) using continuous positiveairway pressure (CPAP) therapy, there is generally provided in the art avent for washout of the bias flow or expired gases to the atmosphere.Such a vent may be provided for example, as part of the mask, or in thecase of some respirators where a further conduit carries the expiratorygases, at the respirator. A further requisite of such masks is thewashout of gas from the mask to ensure that carbon dioxide build up doesnot occur over the range of flow rates. In the typical flow rates inCPAP treatment, usually between 4 cm H₂₀ and 20 cm H₂₀, prior artattempts at such vents have resulted in excessive noise causingirritation to the user and any bed partners.

Various approaches have been developed in the prior art to attempt toreduce the noise when CPAP therapy is provided. For example, in PCTPatent Application No. WO98/34665 it has been proposed that the ventinclude a resilient plug with rounded edge apertures to reproduce noise.However, this is not entirely effective in eliminating the extra noisecreated by a vent at the mask.

In common with all attempts to improve the fit, sealing and user comfortis the need to avoid a concentrated flow of air at any portion of therespiratory tracts. In particular with oral masks or mouthpieces it is adisadvantage of prior art devices that the oral cavity may become overlydehydrated by use of the device, causing irritation and possible latercomplications.

SUMMARY OF THE INVENTION

It is an object of the present invention to attempt to provide a patientinterface which goes some way to overcoming the abovementioneddisadvantages in the prior art or which will at least provide theindustry with a useful choice.

Accordingly, in a first aspect the present invention consists in adevice for delivering a supply of gases to a patient comprising orincluding:

a patient interface fittable to said patient's nose or mouth, which inuse is in fluid communication with said supply of gases,

connecting member having two ends and interface means, one end of saidtwo ends being locatable within said patient interface and the other endof said two ends is connectable to said supply of gases, said membercapable of being fixed into one of two positions, a first position wheresaid member is freely rotatable within said patient interface, and asecond position where said interference means prevents the free rotationof said member within said patient interface.

In a second aspect the present invention consists in a continuouspositive airways pressure system for delivering gases to a patientcomprising or including a pressurised source of gases, transport means,in fluid communication with said pressurised source, adapted to conveysaid gases, and a nasal mask in fluid communication with said transportmeans, in use, delivering said gases to said user, said nasal maskcomprising or including:

a body portion having an inlet, connected to said transportation meansby a connecting member,

sealing means engaged with said body portion, and adapted to sealagainst the facial contours of said patient, and

securement means attached to or around the head of said user,

wherein said connecting member has two ends and interference means, oneend being locatable within said patient interface and the other end ofsaid two ends connectable to said transportation means, said connectingmember capable of being fixed into one of two positions, a firstposition where said member is rotatable within said patient interface,and a second position where said interference means prevents the freerotation of said member within said patient interface.

In a third aspect the present invention consists in a device fordelivering a supply of gases to a patient comprising:

a patient interface, which in use is in fluid communication with saidsupply of gases,

connecting member that connects said patient interface with said supplyof gases,

outlet means associated with said connecting member, said outlet meansincluding at least one outlet vent and a funnel, which in use directsand passes a substantial portion gases expired from said patient throughsaid at least one outlet vent.

To those skilled in the art to which the invention relates, many changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

One preferred form of the present invention will now be described withreference to the accompanying drawings in which:

FIG. 1 is a block diagram of a humidified positive pressure ventilationsystem as might be used in conjunction with the present invention,

FIG. 2 is an illustration of the nasal mask in use according to thepreferred embodiment of the present invention,

FIG. 3 is a side elevation view of an example of a connector used with abreathing circuit,

FIG. 4 is a perspective view from above of a mouthpiece that may be usedwith the elbow connector of the present invention,

FIG. 5 is a perspective view from one side and from an inward directionof the mouthpiece of FIG. 4,

FIG. 6 is a cross-section of the mouthpiece of FIG. 4,

FIG. 7 is a cross-sectional view of the mouthpiece of FIG. 4 and a userwith the mouthpiece in place to demonstrate the location and positioningthereof in relation to the main features of the patient's anatomy,

FIG. 8 is a perspective view of the mouthpiece with an outer flap inplace,

FIG. 9 is a perspective view of the outer flap bent back,

FIG. 10 is a cutaway view of the mouthpiece with the outer flap in use,

FIG. 11 is a perspective view of the outer flap including theventilation apertures and moisture barrier,

FIG. 12 is a front view of a nasal mask, including a swiveled elbowconnection of the present invention,

FIG. 13 is a side view of the swiveled elbow connection as attached tothe mask body of the present invention in a first position,

FIG. 14 is an exploded side view of the locking mechanism part of theswiveled elbow connection in the first position,

FIG. 15 is a side view of the swiveled elbow connection as attached tothe mask body of the present invention, in a second position,

FIG. 16 is an exploded side view of the locking mechanism part of theswiveled elbow connection in the second position,

FIG. 17 shows a nasal mask body and elbow connector with diffuser,

FIG. 18 shows a cutaway side view of the bias How director of thepresent invention, and

FIG. 19 shows a cutaway perspective view of the bias flow director ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides improvements in the delivery of positivepressure ventilation therapy. In particular a patient interface isdescribed which is quieter for the user to wear and reduces the sideleakage as compared with the prior art. The patient interface of thepresent invention includes improvements to the swivel elbow connector,bias flow directional funnel and/or elbow diffuser. It will beappreciated that the patient interface as described in the preferredembodiment of the present invention can be used in respiratory caregenerally or with a ventilator but will now be described below withreference to use in a humidified positive pressure ventilation system.It will also be appreciated that the present invention can be applied toany form of patient interface including, but not limited to, nasalmasks, oral masks and mouthpieces.

With reference to FIG. 1 a humidified positive pressure ventilationsystem is shown in which a patient 1 is receiving humidified andpressurised gases through a patient interface 2 connected to ahumidified gases transportation pathway or inspiratory conduit 3. Itshould be understood that delivery systems could also be YPAP (VariablePositive Airway Pressure) and BiPAP (Hi-level Positive Airway Pressure)or numerous other forms of respiratory therapy. Inspiratory conduit 3 isconnected to the outlet 4 of a humidification chamber 5, which containsa volume of water 6. Inspiratory conduit 3 may contain heating means orheater wires (not shown), which heat the walls of the conduit to reducecondensation of humidified gases within the conduit. Humidificationchamber 6 is preferably formed from a plastics material and may have ahighly heat conductive base (for example an aluminium base) which is indirect contact with a heater plate 7 of humidifier 8. Humidifier 8 isprovided with control means or electronic controller 9 which maycomprise a microprocessor based controller executing computer softwarecommands stored in associated memory.

Controller 9 receives input from sources such as user input means ordial 10 through which a user of the device may, for example, set apredetermined required value (reset value) of humidity or temperature ofthe gases supplied to patient 1. The controller may also receive inputfrom other sources, for example temperature and/or flow velocity sensors11 and 12 through connector 13 and heater plate temperature sensor 14.In response to the user set humidity or temperature value input via dial10 and the other inputs, controller 9 determines when (or to what level)to energise heater plate 7 to heat the water 6 within humidificationchamber 5. As the volume of water 6 within humidification chamber 5 isheated, water vapour begins to fill the volume of the chamber above thewater's surface and is passed out of the humidification chamber 5 outlet4 with the flow of gases (for example air) provided from a gases supplymeans or blower 15 which enters the chamber through inlet 16. Exhaledgases from the patient's mouth are passed directly to ambientsurroundings.

Blower 15 is provided with variable pressure regulating means orvariable speed fan 21, which draws air or other gases through blowerinlet 17. The speed of variable speed fan 21 is controlled by electroniccontroller 18 (or alternatively the function of controller 18 could becarried out by controller 9) in response to inputs from controller 9 anda user set predetermined required value (preset value) of pressure orfan speed via dial 19.

Nasal Mask

A nasal mask that nay be used with the improvements to the swivel elbowconnector, bias flow directional funnel and/or elbow diffuser of thepresent invention is shown in FIG. 2. The mask includes a hollow body102 with an inlet 103 connected to the inspiratory conduit 3. The mask 2is positioned around the nose of the user 1 with the headgear 108secured around the back of the head of the patient 1. The restrainingforce from the headgear 108 on the hollow body 102 and the forehead rest106 ensures enough compressive force on the mask cushion 104, to providean effective seal against the patient's face.

The hollow body 102 is constructed of a relatively inflexible material,for example, polycarbonate plastic. Such a material would provide therequisite rigidity as well as being transparent and a relatively goodinsulator.

The improved swivel elbow connector, bias flow directional funnel and/orelbow diffuser of the present invention may also be used with amouthpiece as described below, or with a full facial mask.

Mouthpiece

Referring to FIGS. 3 to 10 a mouthpiece that may utilise theimprovements to the swivel elbow connector, bias flow directional funneland/or elbow diffuser. In this embodiment, the mouthpiece 50 includes avestibular shield 49 being a generally flat and generallyrectangularly-shaped member in front elevation having a curved profilethat reflects the curvature of a patient's jaw and in turn the curvatureof the labial vestibule region A gases passageway extends through thevestibular shield from an inlet 51 to an outlet 52 in much the same wayas with the earlier embodiments. The inlet 51 is provided by a flattenedoval-shaped connector 53. The outlet 52 has an even more laterallyextended flattened oval shape 54. Most prominently, the mouthpiece 50includes a tongue depressor 55 extending from the inner face of thevestibular shield 49. The operation of the tongue depressor will bedescribed further on with reference to FIG. 5. The tongue depressorincludes a vertical stiffening flange 56 centrally located on its uppersurface and extending from the gases outlet 52. In use gases flow easilyaround the stiffening flange 56 effectively bifurcating the gases outlet52. The tongue depressor 55 further includes a pair of verticallyextending spacers 57, which in use may abut against the roof of thepatient's mouth and ensure that the tongue cannot completely block theair passageway. In the mouthpiece 50 the scaling effect of thevestibular shield 49 against the lips of the user is enhanced byproviding teeth abutments of significantly increased thickness than theraised area 20 of the earlier embodiments. In particular, an upper teethabutment 58 and a lower teeth abutment 59 are provided, with the lowerteeth abutment 59 protruding further from the inner face of thevestibular shield 49 than the upper teeth abutment 58. This differenceserves to match the typical over-bite of most users. The abutments 58and 59 are not required to he wider than the gases outlet 52.

A notch 60 is provided centrally in the upper edge of the vestibularshield 49 to accommodate the upper frenal attachment. A slight bead 61is provided around the edge of the vestibular shield 49 for usercomfort, with the vestibular shield 49 otherwise being very thin foradditional suppleness.

Referring particularly to FIG. 6, the mouthpiece 50 is preferably formedby over-moulding a soft and supple material part 70 over a stiffermaterial part 67. These can generally be termed the shield part and thepassageway-forming insert. The passageway-forming insert preferablyincludes a pair of upper and lower vertical flanges 63 and 64 to fullyengage within the supple material. The passageway-forming insert 67includes the vertically extending stiffening flange 56 of the tonguedepressor 55, together with a curved planar portion 71 forming thebackbone of the tongue depressor 55. The vertically extending spacers 57are of the soft and supple material and arc part of the over-moulding70, as are the upper and lower teeth abutments 58 and 59.

Referring now to FIG. 7, use of the mouthpiece according to FIGS. 4 to 6is depicted. With the present mouthpiece 50, the upper and lower lips85, 86 are further distended by the abutment action of the abutments 75,76 against the upper and lower teeth 87, 88 respectively, thus forming aseal of greater pressure between the lips 85, 86 and the upper and lowerportions respectively of the vestibular shield 49. A lower face 77 ofthe tongue depressor 55 impinges if necessary on the upper surface 72 ofthe tongue 85 and retains the tongue in the lower portion of the mouth.This ensures a clear gases outlet 52 from the gases passageway throughthe vestibular shield. The vertically extending spacers 57, if forced bypressure from the tongue, will engage against the roof of the patient'smouth and maintain a clear air passageway. This stops the sleepingpatient unconsciously blocking the oral passageway and reverting tonasal breathing.

Referring now to FIG. 8 of the present invention is illustratedincluding an extra-oral sealing flap 110. The flap 110 in its naturalbias is tapered, the wide-open end of which is shaped to conform to thefacial contours around the outside of the mouth of a user. The narrowend joins to a cylindrical section, which is designed to slide over theinlet port 114 of the mouthpiece 112. While this is one method ofattachment the flap 100 might also be constructed as an integral part ofthe mouthpiece 112. The flap 110 needs to be constructed of flexiblematerial. Therefore, materials such as silicone rubber can be employedto fashion the flap.

The outer flap 110 is seen in FIG. 9, in a bent back position. It willbe appreciated that when the mouthpiece 112 is being inserted into themouth of a users the outer flap 110 is intended to be in this bent backposition to aid insertion. Prior to insertion, the outer flap is bentback by simply pressing on its outer periphery 116, until it snaps intothe bent back position, in which it will stay unaided.

In FIG. 10 we see the outer flap 110 in use with the mouthpiece 112 inthe mouth 117 of a user 120. Once correctly positioned in the mouth 116,the outer flap 110 may be adjusted into its operational position bypressing on its outer periphery 116 until it snaps back to press againstthe outside of the mouth 118. Due to the relative position of thevestibular shield 122 and the outer flap 110, the outer flap 110 isunable to fully reach its natural bias and thereby inflicts acompressive force on the outside of the mouth 118.

It will be appreciated that as well as providing a substantiallyairtight seal the addition of the outer flap provides enough compressiveforce on the mouth to keep the mouthpiece and conduit in place withoutthe need for straps. This allows the administering of positive airwaypressure ventilation therapy to be considerably less obtrusive thantraditional methods.

In a further additional improvement shown in FIG. 11, the outer flap 300is shown in perspective. Included are ventilation apertures 302, 303either side of the gases port 304, which arc surrounded by a ridge 306acting as a moisture barrier. The apertures 302, 303 are provided suchthat any excess moisture leaking from the mouth will migrate to theapertures where they may evaporate. Small vents in the conduit may beused to direct small amounts of pressurised gas at the apertures to aidevaporation. The ridge 306 is included to ensure that no moisturemigrates further into the scaling region 308, as this would bedetrimental to the sealing properties of the flap.

Interface Connection

Attention is now directed to FIG. 3. It has been found that anadditional factor in the effectiveness of any patient interface 2, isthe manner in which the interface is connected to the breathing circuit.The weight of the breathing circuit, and any attempted movement of oneother of the breathing circuit and the interface 2 relative to theother, is one of the largest influences tending to dislodge theinterface 2. It must be noted that the interface 2 must remain inposition and maintain a seal during all sleep, when the user has nomuscle tone.

The connection is usually provided between a breathing circuit and aninterface 2, which decouples the interface 2 from the breathing circuit.This type of configuration is shown in FIG. 3, where the interface is amouthpiece, although a nasal mask may be used in place of themouthpiece. The connection 40 is effective in reducing the forces placedon the interface 2 by the breathing circuit 41 when the user movesaround during sleep.

To connect between the gases outlet 42, which is vertical when the useris lying on his or her back, and the breathing circuit 41, which isgenerally horizontal, a L-shaped elbow connector 45 is incorporated inthe connection 40. The elbow connector 45 may be incorporated in theinterface 2. The elbow connector 45 is formed at a right angle andprovides a positive pressure on the interface 2. The elbow connector 45may include a swivel joint and may be disconnected from gaseous outlet42. The connection 40 further includes a connecting tube 46 providedbetween the elbow 45 and the breathing circuit 41. The connecting tube46 is preferably connected to the breathing circuit 41 by a swivel joint48 for reasons described herein. The breathing circuit 41, whileflexible, will necessarily be stiff enough to maintain its inter overcomparatively long turns, while the flexible connecting tube 46, beingonly a short length, for example 10 centimeters, merely has to spanbetween the patient's mouth and chest, and can thereby be made in amanner that would not be suitable for long runs. Furthermore, as aresult of the short length of the connecting tube 46, the connectingtube 46 does not need to incorporate significant insulation or heatingcapability. The connecting tube 46 may be formed from a thin plasticmembrane supported over helical or double helical or corrugatedsupporting ribs. In such a case, the support makes the connection tube46 laterally flexible and resistant to torsion. The elbow swivelconnector 45 allows for movement of the connection tube 46 relative tothe interface 2. The swivel connector 48 allows for movement of theconnection tube 46 relative to the breathing circuit 41. It is to beunderstood that one or both of the swivel joints 45, 48 could beeliminated, but the preferred embodiment includes elbow swivel connector48.

Fixable Swivel Joint

The nasal mask or mouthpiece as described above can be provided with animproved L-shaped elbow connector similar to that described above.Referring to FIGS. 12 to 16 a L-shaped elbow 401 is fixed to the maskbase 402 on the nasal mask although not shown in the Figures to inlet 51of the mouthpiece 50. Hereinafter when reference is made to “mask body”or “mask base 402” it is intended to refer to either the mask body orinlet 51 of the mouthpiece. A portion 403 of the elbow connector can berotated about a point X in the directions of arrows A and B. The elbowconnector 401 is connectable at its end 404 to the breathing circuit orconduit 3 as described with reference to FIGS. 1 and 2. The connector401 is designed to be fixed into one of two positions and is able to befully removed from the mask base 402. If the connector 401 is assembledin a first position, it is able to freely swivel, as indicated by thearrows labeled A and B on FIG. 12. If the elbow is pushed into a secondposition, an area of interference prevents the connector from freelyswiveling.

Attention is now drawn to FIGS. 13 and 14 where he mask body 501 andelbow connector 502 are shown in a first position where the connector502 is able to freely rotate 360 degrees about a vertical axis out ofthe mask body. The connector 502 is connected to an aperture in thecentre of the mask body, so that in use, gases flow from the breathingcircuit through the elbow connector and aperture in the mask body andinto the patient's lungs. The elbow connector 502 is held within theaperture in the mask body 501 by way of tubular connector 503 located onthe arm of the elbow connector 502. The tubular connector 503 comprisesvarious ridges and protrusions, moulded in the external surface of theelbow connector's arm, that meet with complimentary ridges andprotrusions moulded in the interior surface of the aperture in the maskbody (or the inlet 51 itself).

In particular, referring to FIG. 14, when the connector 502 is in theposition as shown in FIG. 13, the ridge 601 and protrusion 602 in theconnector 502 act with the small ridge 603 and protrusion 604 in theinterior surface of the mask body, to lock the elbow connector 502 intoa position that enables the elbow to swivel freely within the mask body.To remove the elbow 502 from the mask body 501 a force in the directionof arrow C (see FIG. 13) must be placed on the elbow so that theprotrusion 602 on the elbow is forced past the protrusion 604 on themask body, thereby releasing the connector 502 from the mask body.

The elbow connector may be pushed downwards to into the mask body to aposition as shown in FIGS. 15 and 16. Here, the protrusion 602 of theelbow has been pushed past the lower protrusion 802 on the mask body 501and sits within a complimentary ridge 801 in the mask. The protrusion604 on the mask abuts the ridge 601 on the elbow connector and theexterior side surface 804 of the elbow connector above the ridge 601abuts the interior surface 805 of the mask aperture. The area ofinterference 803 between these surfaces prevents the elbow from freelyswiveling within the mask.

The improvements, as described above, to the elbow connector of thepresent invention provides an attachment that can either freely rotate,or be locked in a particular position according to the patient'sdesires. The improvement to the prior art swivel connectors is that theshort flexible tubing (46 as described with reference to FIG. 3) is nolonger required.

Flow Diffuser and Bias Flow Directional Funnel

In an alternative form of the present invention, and in order to reducethe noise caused by expiratory gases being expelled from the mask ormouthpiece, either may be provided with an elbow connector having adiffuser. In prior art systems the flow diffuser is usually providedwithin the elbow connector at the point of connection to the mask bodyor inlet to the mouthpiece, in the present invention it is envisaged toprovide a diffuser on the elbow connector. The following descriptionrefers to nasal mask when describing the diffuser. The diffuser may alsobe provided with an elbow connector used with a mouthpiece as previouslydescribed.

FIG. 17 shows a nasal mask 901 and elbow connector 902 as that has adiffuser located along the length of the connector 902 previously. Theelbow connector 902 includes a diffuser 903 on its exterior surface, thediffuser is a duct that provides for the broadening of the airflow andreduction in the airflow speed. In the preferred form the duct hasoutlet vent holes 904, 905 and the duct is made out of flexible rubbermaterial. Note must be made that any number of vent holes may beprovided in the duct, the preferred form shown in FIG. 17, merely showstwo vents. The duct is preferably provided with a bias flow directionalfunnel, which will be described below.

Referring to FIGS. 18 and 19, during positive pressure ventilationtreatment a portion of the inlet air flow breathed by the patient isexhausted directly through the bias holes 1001, 1002. The only ventingrequired is to clear the expired CO₂ gas from within the elbow connector902. Therefore a funnel 1004 is provided within the elbow connector 902that directs the exhaled CO₂ gases to the bias holes 1001, 1002 but doesnot direct the inlet airflow from the ventilation machine out the biasholes.

The purpose of the funnel is to vent exhaled air from the breathingsystem to remove CO₂ gases. With the prior art breathing systems it hasbeen found that there is continuous leaking of gases through the ventholes during inspiration and expiration by the patient. Therefore, aloss of pressure occurs due to escaping air. Thus, on inspiration thepatient receives less pressure and thus less breathing therapy, andtherefore this requires that vent holes are provided that are as smallas possible to lessen this effect.

During expiration by the patient it is preferred that most of theexhaled gases are vented through the vent holes, in order to preventpressure spikes and to ensure CO₂ gases are expelled from the breathingtubing. The funnel therefore provides for shielding of the vent holesduring inspiration, but enhances the venting of CO₂ gases by providingdirectional flows during expiration, this also allows for vent holes tobe increased in size, providing larger exhaust areas.

Inlet airflow E flows from the ventilating system through the elbowconnector 902 in the direction of arrows F, G and H and into thepatient's lungs. The air that is exhaled, as indicated by arrow I, flowsthrough the funnel 1004 that has been moulded within the interior of theelbow connector 902. The funnel 1004 is tubular in shape and providesfor the funneling of the exhausted CO₂ gases through the outlet biasholes 1001, 1002. In use, the elbow connector 902 takes the place ofelbow connector 45 which is shown in FIG. 3. Therefore, in use, thefunnel 1004 is located in and extends along the portion of the elbowconnector 902 which is substantially vertical when the patient is lyingon his or her back wearing the patient interface 2.

Providing such a diffuser on the elbow connector effectively minimisesthe noise generated by the outward flow of expiratory gases from themask. The diffuser of the present invention requires little or nomaintenance and improves user comfort. The providing of a directionalfunnel within the elbow connector further minimises noise and reducespressure spikes during exhalation.

What is claimed is:
 1. A patient interface for use as part of a systemfor delivering a supply of gases to a patient comprising: a hollow bodyadapted to locate onto the face of a user in use, said hollow bodyincluding an aperture passing from the inside of said body to theoutside, an elbow connector that connects between said aperture and saidsupply of gases, so that in use the inside of said body is in fluidcommunication with said supply of gases through said elbow connector,said elbow connector having a funnel located within said elbowconnector, and as least one outlet bias hole, said funnel adapted sothat in use a substantial portion of gases expired from said patientpass through said funnel and pass out of said patient interface throughsaid at least one outlet bias hole, said funnel extending within saidconnecting member and shielding said at least one outlet bias hole fromgases supplied to said patient by said supply of gases, said funnelmolded within the interior of said elbow connector, said funnel locatedin and extending along that portion of said elbow connector which issubstantially vertical when said patient is lying on his or her backwearing said patient interface, said funnel extending from said at leastone bias vent hold to a point at or close to said connection betweensaid elbow connector and said hollow body.
 2. A patient interface asclaimed in claim 1 wherein said elbow connector is adapted to locate insaid aperture in use and connect with said body, said elbow connectorand said body further adapted so that in use said elbow connector can beswiveled relative to said body.
 3. A patient interface as claimed inclaim 2 wherein said elbow connector further includes a flexible ductportion on the exterior surface of said elbow connector over and aroundsaid at least one outlet bias hole, at least one outlet vent hole formedin said flexible duct portion.
 4. A patient interface as claimed inclaim 3 wherein said patient interface is a nasal mask.
 5. A patientinterface as claimed in claim 3 wherein said patient interface is amouthpiece.
 6. A patient interface for use as part of a system fordelivering a supply of gases to a patient comprising: a hollow bodyadapted to locate onto the face of a user in use, said body comprising arigid portion that includes an aperture passing from the inside of saidbody to the outside; a mask cushion portion, connected to said hollowbody and in use substantially sealing against said user's face; an elbowconnector located in said aperture so that in use the inside of saidbody is in fluid communication with said supply of gases through saidelbow connector, said elbow connector able to swivel relative to saidbody, said elbow connector including a funnel located within said elbowconnector, and at least one outlet bias hole, said funnel adapted sothat in use a substantial portion of gases expired from said patientpass through said funnel and pass out of said patient interface throughsaid at least one outlet bias hole, said funnel extending within saidelbow and shielding said at least one outlet bias hole from gasessupplied to said patient by said supply of gases, said funnel moldedwithin the interior of said elbow connector which is substantiallyvertical when said patient is lying of his or her back wearing saidpatient interface, said funnel extending from said at least one biasvent hole to a point at or close to said connection between said elbowconnector and said hollow body.
 7. A patient interface as claimed inclaim 6 wherein said patient interface is a nasal mask and said elbowconnector further includes a flexible duct portion on the exteriorsurface of said elbow connector over and around said at least one outletbias hole, at least one outlet vent hole formed in said flexible ductportion.
 8. A patient interface as claimed in claim 6 wherein saidfunnel includes a tubular extension extending from within said elbowconnector, from said at least one outlet bias hole.